[R] Clustering quality measure

[Jonck van der Kogel]

Hi all,
I am running a series of experiments where after manipulating my data I 
run several clustering algorithms (agnes, diana and a clustering method 
of my own) on the data. I wanted to determine which clustering method 
did the best job, so therefore I had defined my own quality measure 
using two criteria: compactness of the data within the clusters 
themselves and the amount of seperation between the clusters. Anyway, 
my quality measure does not work, since according to my quality measure 
the quality gets increasingly better as more clusters are formed untill 
every data instance is a cluster by itself.
Therefore I was wondering if any of you are aware of any libraries or 
functions within R that determine quality measures of clusterings, I am 
very much intrigued by the definition of quality measures that do work.
Thanks very much, Jonck